Rebuild the UI as an app shell: left sidebar, media gallery, structured events

Replaces the centered single-column of full-width cards with a proper application layout: a persistent left sidebar (Trees, and per-tree People/Sources/Media, with the tree name and sign-out) and a constrained content column. Marketing landing and auth pages are split out (own header/footer; centered auth with the logo).

Adds a Media gallery (upload + image thumbnails / file tiles, served via the backend content endpoint). Events are no longer free-text: a curated event-type list (+ custom) and a structured date (qualifier + day/month/year) that composes a proper genealogical date. Regenerated the OpenAPI client.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

frontend/app/register/page.tsx

@@ -34,7 +34,13 @@ export default function RegisterPage() {
   }
 
   return (
-    <Card className="mx-auto max-w-md">
+    <div className="grid min-h-screen place-items-center px-4 py-10">
+    <div className="w-full max-w-md space-y-6">
+    <Link href="/" className="flex justify-center" aria-label="Provenance — home">
+      {/* eslint-disable-next-line @next/next/no-img-element */}
+      <img src="/provenance-logo-plain.svg" alt="Provenance" className="h-8 w-auto" />
+    </Link>
+    <Card>
       <CardHeader>
         <CardTitle>Create your account</CardTitle>
       </CardHeader>
@@ -78,5 +84,7 @@ export default function RegisterPage() {
         </p>
       </CardContent>
     </Card>
+    </div>
+    </div>
   );
 }